This invention relates to battery packs for electric/hybrid vehicles and, more particularly, to a cooling system for a battery pack that provides a substantially uniform cooling of the batteries within the pack by providing a controlled airflow path.
It is well known in the art of electric/hybrid vehicles to provide a battery pack that includes a number of individual batteries to provide the necessary energy to drive the vehicle. When such a battery pack is charged or discharged, heat is produced which, if uncontrolled, can have a significant impact on the life and performance of the pack as a whole as well as the individual batteries that form the pack. Maintaining the temperature of the batteries, individually and as a group, within a defined operating range is essential in maximizing the performance and longevity of the battery pack.
To maintain the batteries at a desired temperature, a cooling system is provided within the pack. Conventionally, cooling systems consisted of passing cool air only over the external surfaces of the batteries. With this type of system, the air picks up heat from battery to battery and loses its cooling capacity. This arrangement inherently creates cooler battery temperatures near the inlet and hotter temperatures near the outlet. Further, the airflow is uncontrolled which also results in unbalanced airflow such that air does not flow past each battery at the same rate and same temperature. As a result, significant temperature variances can occur from one battery to the next, which is detrimental to the battery pack""s performance and longevity. Therefore, it is desirable to provide a cooling system that provides a more even cooling of the batteries.
The present invention provides a battery pack for an electric/hybrid vehicle, which includes a cooling system that uniformly cools the batteries within the pack by providing a controlled airflow path. The battery pack includes a base that supports batteries that are stacked in layers one atop the other. Each battery includes individual integral cells. The batteries are held in spacers that are disposed above and below each layer of batteries. The spacers also provide air passages above and below the batteries to allow cool air to flow across the top and bottom surfaces of the batteries. A retention frame overlays and is affixed to the batteries to restrict the movement of the batteries within the pack. An inlet admits air into the pack and an outlet releases air from the pack after it is has passed through the stack of batteries. A front manifold is connected to the inlet, which includes a plurality of separate runners for evenly splitting the air between the spacers below each layer of batteries. Vertical channels are located between the cells of each battery to allow cooling air to flow between the cells from the spacers below each layer of batteries to the spacers above each layer of batteries. A back manifold directs air from the spacers above each layer of batteries toward the outlet of the pack.
In one embodiment of the present invention, the spacers above and below the batteries are divided into sections that form the rows in which the batteries are placed. Each section includes end walls and side walls which may be shared with an adjacent section. A horizontally disposed edge portion extends outwardly from the walls within each section. The bottom edges of the batteries are seated against the edge portion when the spacer is located beneath the batteries and the edge portion rests upon the top edges of the batteries when the spacer is located above the batteries, thereby creating air passages above and beneath the batteries. Also, a sheet of material is placed between the spacers to define the air passages.
The front manifold runners have a shape that tapers from one end toward an opposite end. Each runner includes slots that correspond with the air passages of the spacers below each layer of batteries. The slots confine the airflow to the air passages of the spacers below each layer of batteries.
The back manifold may also include a plurality of separate runners that taper from one end toward an opposite end. Each runner also includes slots that correspond with the air passages of the spacers above each layer of batteries and further includes baffles that are adjustable between various open and closed positions to regulate the amount of air exiting from each air passage. The air is directed to the outlet of the pack through the back manifold and then through air channels located in the base underneath the battery stack.
The above configuration essentially allows each battery to be cooled through controlled parallel paths. The air does not just flow over the top and bottom surfaces of the batteries, but also flows through the vertical channels between the cells of each battery. Such a cooling system design provides an even temperature distribution throughout the battery pack, resulting in increased life and efficiency of the batteries. An increase in battery life decreases expensive battery pack replacements during the life of a vehicle and an increase in efficiency provides larger driving ranges on a single battery pack charge. Further, the present invention also reduces cost by combining the cooling system, or air passages, with the required structural members.
These and other features and advantages of the invention will be more fully understood from the following description of a certain specific embodiment of the invention taken together with the accompanying drawings.